1. Field of the Invention
The present invention relates generally to cell broadcast services in TDMA (Time Division Multiple Access) mobile communication systems and, in particular, to a TDMA mobile terminal capable of receiving a cell broadcast service even in a speech dedicated mode, and a method for controlling the same.
2. Description of the Related Art
Today, many communication service providers support a cell broadcast service for providing the subscribers with cell broadcasting information such as, for example, weather information and traffic information. The cell broadcast information is transmitted from a base station to mobile stations (i.e., mobile terminals) only in a cell broadcast dedicated mode through a SDCCH(2) channel (Stand alone Dedicated Control Channel 2). The SDCCH(2) channel is commonly referred to as a SDCCH subchannel 2. The SDCCH(2) channel is used for the connection for signaling between the mobile station and a network. This connection is necessary for a position updating function and other management functions.
In receiving the cell broadcast service, upon power-up, the mobile station analyzes system information transmitted from the base station to check whether or not the received system information includes cell broadcast information. When the received system information includes cell broadcast information, a dedicated channel is allocated for the mobile station. The mobile station receives the cell broadcast information by opening a window in the SDCCH(2) channel of the dedicated channel which includes the cell broadcast information. The received cell broadcast information is then displayed through a display.
A conventional GSM (Global System for Mobile communication) terminal performs receiving, transmitting and monitoring operations in sequence for one TDMA frame (of about 4.615 ms) consisting of eight time slots. Therefore, in the speech dedicated mode (wherein the user talks with another party), the mobile station cannot receive the cell broadcast information.
FIG. 1 is a diagram illustrating the structure of a conventional unit TDMA frame. In FIG. 1, since a time slot TS0, an interval represented by Rx, is dedicated to the cell broadcast service and signaling, the user cannot talk with another party during time slot TS0. Therefore, the user should talk over the telephone using a frequency of a call dedicated channel and a newly allocated time slot number.
As stated above, two dedicated receiving channels are simultaneously required to receive the cell broadcast service and a call. However, a conventional GSM terminal does not simultaneously support both the call and the cell broadcast service. Occasionally, particularly when having a telephone conversation with the terminal placed on the cradle of a hands free kit, the user may need to receive cell broadcast information even in the speech dedicated mode.
It is therefore an object of the present invention to provide a TDMA mobile terminal capable of receiving a cell broadcast service even in a speech dedicated mode.
To achieve the above and other objects, a TDMA (Time Division Multiple Access) mobile terminal having a display is provided. The TDMA terminal comprises: a controller for receiving cell broadcast information on a dedicated channel using time slots remaining after subtracting (also known as excepting) time slots necessary for a call from one TDMA frame, and for displaying the received cell broadcast information on the display regardless of a current operation mode.
These and other objects, features and advantages of the present invention will become apparent from the following detail description of illustrative embodiments thereof, which is to be read in connection with the accompanying drawings.